I installed one in my -4 in place of a voltmeter. Super easy installation and works great. The case is threaded. It takes minutes to screw in an existing 2 1\4 instrument hole.
I really like all of the functions (clock, voltmeter, g-meter, timer, flight time) and the ease of use. I wish it displayed the max and min G without having to press a button. That's the only gripe I have.
I'd recommend it and would buy it again for a plane that didn't have an EFIS with those functions built in.